Using underscore to ignore elements in a destructuring tuple assignment is flagged as a syntax error

[rben01]

rust-analyzer version: ba3305480 2022-02-07 stable

rustc version: rustc 1.60.0-nightly (08df8b81d 2022-01-30)

When using tuple destructuring assignment without a let, i.e., when assigning to existing variables and not binding new variables, RA incorrectly flags it as a syntax error. The code below actually compiles fine.

let x;
let y;
(x, _, y, _) = (1, 2, 3, 4); // <-- half of this line is flagged with various "expected X" errors

// not flagged
let (x, _, y, _) = (1, 2, 3, 4);

[Veykril]

I think we don't support destructuring assignment at all yet, so this gets parsed as a binary expression with the LHS being parsed as an expression as well.
(I believe there is an issue about that already but I can't find it).